The present invention relates to transmission of data in a network environment. More specifically, the present invention relates to methods and apparatus for improving the efficiency with which data are transmitted over the Internet. Still more specifically, the present invention provides techniques for providing differentiated services for such transmitted data.
Generally speaking, when a client platform communicates with some remote server, whether via the Internet or an intranet, it crafts a data packet which defines a TCP connection between the two hosts, i.e., the client platform and the destination server. More specifically, the data packet has headers which include the destination IP address, the destination port, the source IP address, the source port, and the protocol type. The destination IP address might be the address of a well known World Wide Web (WWW) search engine such as, for example, Yahoo, in which case, the protocol would be TCP and the destination port would be port 80, a well known port for HTTP. The source IP address would, of course, be the IP address for the client platform and the source port would be one of the TCP ports selected by the client. These five pieces of information define the TCP connection.
Given the increase of traffic on the World Wide Web and the growing bandwidth demands of ever more sophisticated multimedia content, there has been constant pressure to find more efficient ways to service data requests than opening direct TCP connections between a requesting client and the primary repository for the desired data. Interestingly, one technique for increasing the efficiency with which data requests are serviced came about as the result of the development of network firewalls in response to security concerns. In the early development of such security measures, proxy servers were employed as firewalls to protect networks and their client machines from corruption by undesirable content and unauthorized access from the outside world. Proxy servers were originally based on Unix machines because that was the prevalent technology at the time. This model was generalized with the advent of SOCKS which was essentially a daemon on a Unix machine. Software on a client platform on the network protected by the firewall was specially configured to communicate with the resident demon which then made the connection to a destination platform at the client's request. The demon then passed information back and forth between the client and destination platforms acting as an intermediary or “proxy.”
Not only did this model provide the desired protection for the client's network, it gave the entire network the IP address of the proxy server, therefore simplifying the problem of addressing of data packets to an increasing number of users. Moreover, because of the storage capability of the proxy server, information retrieved from remote servers could be stored rather than simply passed through to the requesting platform. This storage capability was quickly recognized as a means by which access to the World Wide Web could be accelerated. That is, by storing frequently requested data, subsequent requests for the same data could be serviced without having to retrieve the requested data from its original remote source.
Unfortunately, interaction with such proxy servers is not transparent, requiring each end user to select the appropriate proxy configuration in his or her browser to allow the browser to communicate with the proxy server. For the large ISPs with millions of customers there is significant overhead associated with handling tech support calls from customers who have no idea what a proxy configuration is. Additional overhead is associated with the fact that different proxy configurations must be provided for different customer operating systems. The considerable economic expense represented by this overhead offsets the benefits derived from providing accelerated access to the World Wide Web. Another problem arises as the number of WWW users increases. That is, as the number of customers for each ISP increases, the number of proxy servers required to service the growing customer base also increases. This, in turn, presents the problem of allocating packet traffic among multiple proxy servers.
Another technique for increasing the efficiency with which data requests are serviced is described in commonly assigned, co-pending U.S. patent application Ser. No. 08/946,867 for METHOD AND APPARATUS FOR FACILITATING NETWORK DATA TRANSMISSIONS filed Oct. 8, 1997, the entirety of which is incorporated herein by reference for all purposes. The invention described in that co-pending application represents an improvement over the proxy server model which is transparent to end users, high performance, and fault tolerant. By altering the operating system code of an existing router, the router is enabled to redirect data traffic of a particular protocol intended for a specified port, e.g., TCP with port 80, to one or more caching engines connected to the router via an interface having sufficient bandwidth such as, for example, a 100baseT interface. If there are multiple caching engines connected to the cache-enabled router, the router selects from among the available caching engines for a particular request based on a simple algorithm according to which a particular group of addresses is associated with each caching engine.
The caching engine to which the request is re-routed “spoofs” the requested destination platform and accepts the request on its behalf via a standard TCP connection established by the cache-enable router. If the requested information is already stored in the caching engine, i.e., a cache “hit” occurs, it is transmitted to the requesting platform with a header indicating its source as the destination platform. If the requested information is not in the caching engine, i.e., a cache “miss” occurs, the caching engine opens a direct TCP connection with the destination platform, downloads the information, stores it for future use, and transmits it to the requesting platform. All of this is transparent to the user at the requesting platform which operates exactly as if it were communicating with the destination platform. Thus, the need for configuring the requesting platform to suit a particular proxy configuration is eliminated along with the associated overhead. Moreover, traffic may be easily allocated among as many caching engines as become necessary. Thus, content caching provides a way to compensate for the bandwidth limitations discussed above. Currently, most Internet service providers (ISPs) accelerate access to their web sites using cache engines.
Another specific embodiment of a packet redirection protocol which may be used to implement such a network caching technique is described in co-pending, commonly assigned, U.S. patent application Ser. No. 09/608,802 for METHOD AND APPARATUS FOR REDIRECTING NETWORK TRAFFIC filed Jun. 30, 2000, the entirety of which is incorporated herein by reference for all purposes. According to a specific embodiment described in that application, the network caches have the capability of determining that particular redirected packets should be transmitted back to the redirecting router and reinserted into the original traffic flow. This may be done in a manner transparent to the source or destination of the packets. An example of a case in which packets would need to be reinserted in the original flow might be where the cache recognizes the source and destination pairs identified by the packets as corresponding to a connection requiring IP-based authentication. Another example would be where the cache is overloaded and is currently unable to handle all of the redirected traffic.
Content providers are also experiencing a need to provide differentiated quality of service to their customers, for example, an e-commerce site may want to provide superior service to its premium customers. A web portal might want to favor paying subscribers over general surfers. A B2B (business-to-business) site may want to provide more reliable web access to its preferred business partners. Since most of these sites deploy web caches (cache engines) in reverse proxy mode in front of their server farm to offload traffic and optimize the entire web site infrastructure, providing differentiated services in cache engines would be highly desirable to enhance the quality of service experienced by the end user.
In view of the above, it would be desirable to provide a cache engine capable of providing differentiated services.